1. Field of the Invention
The present invention relates to remote control systems, and more particularly, to a method capable of universally decoding remote control commands and associated apparatus.
2. Description of the Prior Art
As electronics technology progresses, all kinds of electronic devices are steadily becoming a part of everyday life in a modern society. Many consumer electronics products, such as televisions, DVD players, and multi-function digital media players are being adopted generally by society. In order to allow a user to operate each function of every consumer electronics product, most of the consumer electronics products come with a remote controller. The remote controller allows the user to control operation of any electronic product.
The prior art infrared control system allows one-to-one control of the electronic device. In other words, every electronic device must have its own corresponding remote control. And, each function that the remote controller operates is governed by a remote control signal that contains information associated with the function. The remote controller has many buttons, each of which controls one of the functions. To engage one of the functions of the electronic device, the user must press the corresponding button to send the remote control signal containing the information associated with that function. When the electronic device receives the remote control signal, the electronic device extracts the information from the remote control signal, and performs the function corresponding to the information in the remote control signal.
Generally speaking, the remote controller employs either infrared or radio frequency technology for transmission. Radio frequency technology does not have a problem of dependence upon transmission direction, and is also bi-directional, such that it not only sends remote control signals, but is also able to receive signals, such as status information, from other appliances, and display the same on a display of the remote control. Infrared technology, on the other hand, has advantages of a smaller size, lower power consumption and low cost. Thus, remote controllers that employ infrared technology dominate a remote control market.
FIG. 1 is a diagram of an infrared remote control system 10 according to the prior art. The infrared remote control system 10 comprises a transmitting end 12 and a receiving end 14. The transmitting end 12 comprises an input interface 120, an encoding module 122, and an infrared transmitter 126. The receiving end 14 comprises an infrared receiver 140, a control module 144, and a functions module 146. At the transmitting end 12, the input interface 120 comprises a plurality of buttons corresponding to different functions, and a user can press the buttons to perform functions of the electronic device. The encoding module 122 converts an output of the input interface 120 to a binary signal, which may include a header or padding bits, according to a predetermined rule, in order to produce a packet complying with a special format. The packet is then transmitted to the receiving end 14 through an infrared beam by the infrared transmitter 126. Contrastingly, at the receiving end 14, the infrared receiver 140 converts the infrared beam from the infrared transmitter 126 to an electronic signal through an optical-to-electrical conversion process. The control module 144 comprises a microcontroller 148 and a memory 150 for demodulating, decoding, and recognizing the control signal sent by the transmitting end 12. The control module 144 downconverts the control signal carried by the infrared beam to a baseband, in order to recognize a control command from the transmitting end 12, and execute corresponding functions F(1) . . . F(n) through the functions module 146 based on the control command.
In the infrared remote control system 10, because only a small amount of information is transmitted from the transmitting end 12 to the receiving end 14, accuracy is the most important consideration when transmitting the information. Many encoding standards have been developed in the prior art. In Europe, two most prevalent standard encoding schemes are an RC-5 standard and an RECS80 standard. In Asia, an NEC standard is prevalent. Besides, many consumer electronics manufacturers, such as Mitsubishi, Panasonic, and JVC, develop proprietary encoding schemes. These encoding schemes can be roughly divided into three modulation methods: phase modulation, pulse width modulation, and pulse position modulation. Please refer to FIGS. 2-4, which are waveforms corresponding to phase modulation, pulse width modulation, and pulse position modulation, respectively. Phase modulation represents a falling edge within a unit time interval by a “0”, and a rising edge within the unit time interval by a “1”. In pulse width modulation (shown in FIG. 3), pulse width determines a “0” and a “1”. For example, in an NEC encoding standard, the “0” represents a pulse that is high for 0.56 ms and low for 0.56 ms, and the “1” represents a pulse that is high for 0.56 ms and low for 1.68 ms. Finally, pulse position modulation (shown in FIG. 4) represents pulses occurring in different positions relative to a reference pulse position by “0” and “1”.
In view of the above modulation methods, the control module 144 requires different demodulation and decoding methods to obtain the control command sent by the transmitting end 12. Taking the pulse width modulation as an example, the microcontroller 148 of the control module 144 uses an internal clock to measure a high period and a low period to identify the “0” and “1” of the received signal. In other words, a decoding process according to the prior art requires the internal clock of the microcontroller 148. Generally speaking, in multimedia devices, in addition to demodulation and decoding, the microcontroller 148 also involves video and audio processing. Thus, the prior art occupies the internal clock hardware resource of the microcontroller 148, which decreases the efficiency of the video and audio processing performed by the microcontroller 144, and deteriorates the multimedia output quality. In view of the above decoding standards, the prior art remote control system use proprietary hardware to realize one of the decoding standards. No flexibility exists in design for system manufacturers. For example, liquid crystal display (LCD) televisions require an infrared receiver, but LCD televisions are sold all over the world. Thus, infrared systems with proprietary decoding schemes are troublesome for various modifications for system manufacturers.